In order to improve the productivities of a yoke and a speaker, a rectangular speaker 101 which is as shown in FIG. 35, and which is assembled by using a yoke 100 such as shown in FIG. 34 is known (see Patent Literature 1).
The yoke 100 shown in FIG. 34 is formed into a bottomed rectangular frame-like shape by bending one sheet-like metal material which is previously punched, to dispose four bent and raised portions 100A.
In the speaker 101 shown in FIG. 35, a rectangular magnet 102 is clamped by the yoke 100 and an upper plate 103 having a rectangular plate-like shape, to constitute a magnetic circuit 104. The yoke 100 of the magnetic circuit 104 is pressingly inserted into a frame 105, and coupled thereto by interposing an adhesive agent between them. A diaphragm 106 is bonded to a peripheral edge portion of the frame 105, a voice coil 107 for driving the diaphragm is coupled to the diaphragm 106, and the voice coil 107 is fittingly coupled into a magnetic gap 108, thereby completing the speaker.    Patent Literature 1: Japanese Patent Application Laying-Open No. 2003-37892